Voltage regulator



Oct. 18, 1938. E. w. swANsoN 2,133,312

VOLTAGE REGULATOR Filed May 25, 1936 v v L T; ,.f. R

'. 3 4 J ,WT INVENTOR. l

. .6a/rm' MJM/a/y BY ,476, J W c'. wurd /7//5` ATTORNEY Patenfedoct. 18,193s VOLTAGE REGULATOR Edwin W. Swanson, Hopkins, Minn., assignor toElectric Machinery Manufacturing Company,

` Minneapolis, Minn.

Application May 25, 1936, Serial N0. 81,705

14 claims.

My invention relatesto voltage regulators for sources of alternatingcurrent and particularly alternating-current generators and has for anobject to provide a voltage regulator` which opcrates with variableload, or variable speed of the generator, or both to maintain asubstantially constant voltage at the source.

A further object of my invention is to provide a voltage regulatorbywhich any degree of over-i` compounding or'undercompounding may beobtained.

Another object of my invention is to provide a voltage regulator whichis characterized by a quick response to changes in the voltage to beregulated. L

Another object of this invention is to produce a voltage regulator whichis inexpensive in construction, simple and reliable in operation, low inmaintenance cost, and easy of adjustment.

These and other objects and advantages of the invention will be fullyset forth in the following description made in connection with theaccompanying drawing, in which like reference characters refer tosimilar parts throughout the 25 several views, and in which:

Fig. 1 is a wiring diagram of an embodiment of my invention `applied toan alternating-current generator;

Fig. 2 is a wiring diagram of a modification of my invention;

Fig. 3 is a conventional representation of the electric phenomena of myinvention;

Fig..4 is a wiring diagram of still another modification of myinvention;

Fig. 5 is a load characteristic diagram of a generator, showing theresults obtainable with my invention.

Referring to Fig. 1 of the drawing, an altermating-current generator isillustrated which is provided with an armature winding I2 and a fieldwinding I3. 'I'he armature winding I2 is connected to analternating-current circuit indicated by the reference character A.Crbymeans of conductors I4 and I5, and a line switch |1. The eld winding|3 is energized with direct current derived from conductors I8 and I9which are connected to a direct-current circuit indicated by thereference character D. C. by means of a field switch 2|. An adjustableresistor or rheostat is connected in series with the field winding I3 inthe conductor i9. The alternate ing-current generator II is driven by aprime mover, not shown in the drawing.

The inventionincludes a relay 22 which comprises a nonmagnetic base 23,a magnetic U- shaped core 24 preferably of laminated construction, arelay winding 25 disposed on the core 24, a magnetic armature 21 of thevibratory type, and an adjustment for the armature 21 comprising aresilient member or leaf spring 28 and an adjusting screw 29 screwed inthe base 23.

The relay winding 25 is connected in a circuit |25 which I havedesignated as the control circuit and which is connected to theconductors |4 `and I5, and is energized by the voltage of the generatorII. A rectier 26, preferably of the copper-oxide type, is connected inthis circuit in series with the winding 25. The armature 21 operates aswitch mechanism |30 which includes two movable contacts 30 and 3|carried by the armature, and two fixed contacts 32 and 33, the contacts30 and 3| being electrically connected together. The switch mechanism|30 is connected in a circuit |34 which I have designated as theregulating circuit. This circuit includes two conductors 34 and 35 whichare connected to contacts 32 and 33 respectively. Conductor 34 isfurther connected to the conductor I9 and vcuit reaches a predeterminedvalue.

which is connected across the fixed contacts 32 and 33. It will readilybe noted that one pair of contacts could be utilized to make and breakthe circuit, but this would materially increase the heating, arcing, andpitting.

The operation of the above embodiment of my invention can best beexplained as follows: The armature 21 is so designed that it willrespond to the variations in current produced by the current pulsesflowing in the control circuit |25. This is made possible by the factthat the current pulses are only fractional-wave and intermittent. Inaddition, the spring 28 is so designed and screw 29 so adjusted thatinitiation of movement of the said armature occurs only, after themagnitude of the current in said cir- Assume that the generator voltagedrops below its normaLValue. Since the rectifier 26 allows current toflow only in one direction and the generator voltage is below normalvalue, the pulsating cur- .rent nowing inthe relay winding 25 will causeage is below normal value. In such case the switch mechanism |30 remainsclosed during the greater portion of each cycle. While the switchmechanism |30 is closed, the rheostat 20 is shortcircuited so that agreater amount of direct current iiows in the eld winding i3 and therebycauses the generator voltage to increase.

Now assume that the generator voltage rises above its normal value. Inthis case, the pulsating current owing in the relay winding 25 willincrease, causing a pulsating magnetomotive force of greater magnitudeto attract the relay armature 2l to the core 2Q. Since the same value ofcurrent is required to attract the relay armature 2l! to the core 2li,the result will be'a pulsating current ofgreater magnitude attractingthe relay armature 21 during a longer dura- A.tion of time, thus holdingthe switch mechanism l30 open during a greater portion of each cycle.This action will be further explained in connection with the diagramshown in Fig. 3. While the switch mechanism is open, the resistor orrheostat 20 is not short-circuited so that a smaller amount of directcurrent flows in the field winding I3 and thereby causes the generatorvoltage to decrease.

Thus by combining the action due to the low voltage and that due to thehigh voltage as explained above, my voltage regulator operates to closeand to open the switch mechanism l30 intermittently but with varyingduration of time during each cycle so as to deliver a direct-currentexcitation to the eld winding which maintains the generator voltagesubstantially constant.

Adjustment for any desired voltage may be had by means of theadjusting'screw 20. By turning the screw 29 to bring increased pressureupon the resilient member or leaf spring 28, the value of the currentrequired to initiate movement of the armature 2l? is increased so thatthe relay operates tomaintain a higher voltage; and vice versa. Aspirally coiled spring attached to the relay armature 2l may also beusedthe adjustment being-obtained by means of a threaded screw and nutarrangement.

A modification of my invention is shown in Figure 2 in which an opposingdirect-current component is added in the pulsating current which owsthrough the relay winding 25. Since this modication is in most respectsidentical with the construction shown in Fig. l, the same referencenumerals will be used to designate similar parts and the descriptionthereof will not be repeated. To supply the added direct-currentcomponent, a resistor 3l is employed which is connected in parallel withthe eld winding i3 by means of a circuit itl. rIhis resistor 3l has -anadjustable tap 38 which divides the resistor into two sections, one ofsaid sections being connected in the circuit H25. 'Ihe rectiiier 2G,relay winding 25, and said section of resistance 3l are all in series inthe circuit |I25 which is connected to conductors lli and l5,

To better explain the action of the direct-cur- .rent component utilizedin my voltage regulator shown in Fig. 2, reference is to be had to Fig.3.

v The zero axis is shown by a straight line o-u, and

Since the rectier 26 prevents the.

ponent merely acts as an opposing electromotive force against theintermittent ow of the alternating current, i, e., during the currentpulses. The resultant current owing in the relay winding 25 is shown bythe heavy wave, oefghiylclmu, which comprises three pulses of pulsatingcurrent, one pulse for each cycle of alternating current. The shadedareas efy, hifi, and klmlepresent the pulses of current which passthrough the relay winding 25 and produce a pulito attract time intervalfrom n to r if no component of direct current is utilized as is the casewith the embodiment of the invention shown in Fig. 1,

or from s to t if the component of direct current l is `ltilized as isthe case with the modification of the invention shown in Fig, 2. In thesystem of Fig. 2 the time interval per cycle during which the armature2l is attracted depends upon the resultant current as represented by theshaded areas. If a greater direct-current component is used, then theresultant current pulses, as represented by the shaded areas, aredecreased which results in a shorter time interval per cycle duringwhich the relay armature 2'? is attracted. This leaves the switchmechanism 930 closed during a greater portion of each cycle, whichoperates to produce increased field excitation and higher generatorvoltage. If a lesser direct-current-component is used, then theresultant current is increased which results in a longer time intervalper cycle during which the armature is attracted, which producesdecreased eld excitation current and lower generatorl voltage. It willbe noted that the switch mechanism l30 is closed'A while the relay 22 isdeenergized, includingthe time intervals g to h and to k, and duringthese intervals the rheostat is short-circuited which results in minimumvalue of resistance and maximum current in the eld circuit. The switchmechanism H30 is open while the relay 22 is energized which occursduring the various current pulses, and during these current pulses,theresistor 20 is not short-circuited which results in connecting theoperative value of resistor 20 in the circuit.

The armature 2l in normal operation of the voltage regulator has avibratory action corresponding to the frequency of the control circuitvoltage. This action may cease if the voltage becomes too low. In suchcase the armature 2l is not attracted to the core 24 and the switchmechanism |30 remains closed. Where the .drop in voltage is onlytemporary, the action of the voltage regulator would be periodic. Suchaction would occur if the generator voltage dropped to a Value below theline p-q of Fig. 3 in which eol etv

case the regulator would perform its maximum duty by continuallyshort-circuiting the rheostat to furnish maximum field excitationcurrent.

In Fig. 4 another modification of my invention is shown which isespecially applicable to large high-voltage alternating-currentgenerators. In this form of the invention a three-phase generator hasbeen shown which is indicated by the reference numeral I 'I'hisgenerator is connected to a three-phase circuit Ycomprising conductorsII4, I|5 and |I6. The relay and certain other features of this form ofthe invention being identical with that shown in Fig. 2, similarreference characters will be used to designate corresponding parts ofelements and the description thereof will not be repeated. This form ofthe invention includes two condensers, 36 and |36', and

. Voperates on the rheostat 4| in the shunt field circuit |45 of adirect-current generator or exciter 42 which supplies the direct-currentexcitation to the field winding I3 of alternating-current generator Il.To further reduce the sparking and pitting of the contacts comprisingthe relay switch mechanism |30, the two condensers 36 and |36 areconnected in series, one across each pair of contacts. The midpointbetween the condensers is electrically connected to the center of therheostat 4| by means of a conductor 43 and to the relay armature 21 bymeans of a conductor 44. 'Ihe shunt field circuit |45 of exciter 42includes a shunt field winding 45, the rheostat 4I, and conductors 46and 41. The exciter output terminals are electrically connected to thefield switch 2| byrmeans of conductors 48 and 49. The form of theinvention shown in'Fig. 4 differs further from the construction shown inFig. 2 in that the control circuit |25 is energized by a potentialtransformer 40 whose -primary is connected to conductors I4 and I5 ofthe threephase circuit. Such potential transformer may also be used withthe forms of invention shown in Figures 1 and 2.

Even though the modification of Fig. 4 is quit similar in many respectsto that shown in Fig. 2,

an explanation of itsV operation may be useful. During normal operation,the alternating-current generator II is driven by a prime mover and thefield switch 2| is closed furnishing directcurrent excitation to thegenerator field winding I3, and the line switch l1 is closed deliveringvalternating current. When the generator voltage drops below the normalvalue, the pulsating current in the'regulator winding 25 decreases asexplained in connection with Fig. 3. This results in a decreasedmagnetomotive force in relay 22 so that the switch mechanism |30 remainsl closed during the greater portion of each cycle to short-circuit therheostat 4|. This increases the shunt field current which serves toincrease the output of exciter 42 and thereby supply increaseddirect-current excitation to the generator field winding I3 whichincreases the-generator voltage. If the generator voltage rises abovethe normal value, the pulsating current in winding 25 increases whichoperatesv to decrease the shunt field current of exciter 42 and therebydecrease the direct-current excitation and the generator voltage.

The curves of Fig. 5 will serve to show the relation of terminal voltageto load amperes of a typical alternating-current generator under fourdifferent conditions. Curve 5| labeled Generator without regulator showsthe normal characteristic of the generator operating without a regulatorand lwith sufficient direct-current excitation to supply 100% terminalvoltage at 0% load amperes. Curve 52 labeled Undercomlpounded shows abetter characteristic than that of curve 5|, since the terminal voltageis held up to a higher value at all loads than that of curve 5| but nothigh enough to maintain a constant voltage with increase of load. Such arelation would be obtained by the use of the form of the invention shownin Fig. l, and it may also be obtained by use of the modifications shownin Figures 2 and 4 by proper adjustment of tap 38 on resistor 31. 'Curve53 labeled Flatcompounded shows the characteristic in which the terminalvoltage is maintained substantially constant from rio-load amperes to100% load amperes, resulting in a substantially fiat curve. Thischaracteristic may be obtained by use of the modifications shown inFigures 2 and 4. Curve 54 labeled Overcompounded shows thecharacteristic in which the terminal Voltage increases with increase ofload from no-load amperes to 100% load amperes, and may be obtained bythe use of the modifications shown in Figures 2 and 4 by properadjustment.

As load is added on the generator, the field excitation current mustincrease in order to maintain substantially constant voltage. Withparticular reference to Figures 3 and 5, the follow-` ing addedexplanation of my invention is given: As the load on the generator isincreased, the alternating-current voltage tends to decrease andtherefore lesserpulses of current tend to flow through the controlcircuit |25, which in turn operates to supply an increased fieldexcitation current and a higher generator voltage as fully explainedheretofore. This increased field excitation current also supplies alarger direct-ourrent component to the control circuit |25 so that lined-c in Fig. 3 drops further away from the zero axis o--u. Thus as thegenerator voltage is restored to normal value, the shaded areas of eachcurrent pulse become smaller which provides a longer'duration of timeper cycle that the contact mechanism |30 remains closed, just as isdesired in order to supply the required directcurrent excitation at allloads. Therefore it is possible to add load until -theexcitation currentbecomes so high that the shaded areas fall below line p-q, resultinginthe drooping characteristic of curves 52, 53 and 54 as shown beyond100% load amperes in Fig. 3.

My voltage regulator is simple in both mechanical and electricalaspects, yet operates at a high degree of accuracy to maintain constantvoltage from no-load to 100% load amperes on an alternating-currentgenerator. Even with a variation in speed, up to 5% of the normal speed,the regulator operates to maintain substantially constant voltage. It isvery inexpensive, easily adjusted, and requires'minimum maintenance.With my invention a continualvibratory action is obtained which providesa sensitive and quick-acting regulator, due to the minimizaltion ofinherent delays necessary in overcoming sistor, since it is obvious toone skilled in the art that the relay 22 may also operate upon the gridof thermionic tubes, or upon a carbon pile rheostat controlling theresistance theref to vary the direct-current excitation supplied to thefield Winding of the generator.

It will, of course, be 4understood that various changes may be made inthe form, details, proportions and arrangements of the parts, withoutdeparting from the scope of my invention, which generally stated,consists in a device capable of carrying out the objects above set forthand in the novel parts and combination of parts. disclosed and definedin the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A voltage regulator comprising a relay including a core, a Windingthereon, and a vibratory armature, an alternating-current controlcircuit energized by the voltage to be regulated, said'winding beingconnected in said control circuit, a rectifier in said control circuitfor supplying intermittent fractional wave current pulses to saidwinding, said armature being capable of movement in. conformity withsaid current pulses, adjustable means for controlling initiation ofmovement of said armature, and means operated by said armature forregulating the voltage.

2. A voltage regulator comprising a relay including a winding and switchmeans, an alterhating-current control circuit energized by the voltageto be regulated, said winding being connected in said control circuitarectifier in said control circuit effecting in said Windingintermittentl fractional wave pulses, a source of uniform direct currentin said control circuit independent of said voltage, a regulatingcircuit, said switch means being connected in said regulating circuit,and means operated by said regulating circuit for varying the voltage tobe regulated.

3. A voltage regulator fora generator having a field winding, saidregulator comprising a relay including a winding and switch means, analterhating-current control circuit energized by' the voltage to beregulated, said winding being connected in said control circuiteffecting in said Winding intermittent fractional Wave pulses, arectifier in said control circuit, a regulating circuit and a resistorconnected in series with said ,field winding and in said regulatingcircuit, said 'switch means being connected in said regulating circuit,said regulating circuit intermittently shunting said resistor once foreach cycle for varying the voltage to be regulated.

4. A voltage regulator comprising a relay including a core, a windingthereon, and a vibratory armature, an alternating-current controlcircuit energized by the voltage to be regulated, said I varying thevoltage to be regulated.

5. A voltage regulator comprising a relay including a core, a windingthereon, and a vibratory armature, an alternating-current controlcircuit energized by the voltage to be regulated, said winding beingconnected in said control circuit, a rectifier in said control circuitfor supplying intermittent fractional wave current pulses to saidwinding, said armature being capable of movement in'conformity with saidcurrent pulses, and means operated by said armature for regulating thevoltage.

6. A Voltage regulator comprising a relay including a core, a windingthereon, and a vibratory armature, an alternating-current controlcircuit energized by the voltage to be regulated, said winding beingconnected in said control circuit, a rectifier in said control circuitfor supplying intermittent fractional wave current pulses to saidwinding, a source of direct current in said control circuit independentof the generator volt- 1 age, said armature being capable of movement inconformity with said current pulses, and means operated by said armaturefor regulating the voltage.

7. A voltage regulator comprising a relay including a winding and switchmeans, an alternating-current control circuit energized by the voltageto be regulated, said winding being connected in said control circuit, arectifier in said control circuit effecting in said winding intermittentfractional wave pulses, a source of direct current in said controlcircuit opposing the ow of current through said rectifier, a regulatingcircuit, said switch means being connected in said regulating circuit,and means operated by said regulating circuit for varying the voltage tobe regulated.

8. A voltage regulator comprising a relay including a core, a windingthereon, and a vibratory armature, an. alternating-current controlcircuit energized by the 4voltage to be regulated, said winding beingconnected in said control circuit, a rectifier in said control circuitforsupplying intermittent fractional wave current pulses to saidwinding, a source of direct current in said control circuit opposing theflow of current through said rectifier, said armature being capable ofmovement in conformity with said current pulses, and means operated bysaid armature for regulating the voltage.

9. A voltage regulator for alternating current comprising a relay, arectifier for supplying intermittent fractional wave current pulses tosaid relay from the voltage to be regulated, said relay acting inconformity with said pulses, and means controlled by said relay andresponsive to the effect of said pulses during the time that the relayis actuated thereby, for regulating the voltage.

10. A voltage regulator for alternating current comprising a relay, arectifier for supplying to said relay intermittent fractional wavecurrent pulses lfrom the voltage to be regulated, said relay acting inconformity with said pulses and such action being initiated when thepulse reaches a certain.v magnitude, and means controlled by said relayand responsive to the effect of said pulses during the time that therelay is actuated thereby for regulating the voltage.

11. A voltage regulator for alternating current .comprising a relay, arectifier for supplying to said relay intermittent fractional wavecurrent 4pulses from the voltage to be regulated, said relay acting inconformity with said pulses and such action being initiated when thepulse reaches a certain magnitude, and a variable resistor having aminimum and operative resistance.

mum resistance of said resistor during the time that said relay isinactive.

12. A voltage regulator for a generator having a iield winding, saidregulator comprising a relay including a winding and switch means, analtermating-current control circuit energized by the voltage to beregulated, said Winding beingconnected in said control circuit, arectifier in said control circuit, a source of direct current forenergizing said eld winding, means responsive to the voltage across saidiield winding for impressing on said control circuit a direct-currentvoltage opposing the ilow of current through said rectifier, and meansoperated by said regulating circuit for regulating the voltage.

13. A voltage regulator for an alternating-current system, saidregulator comprising a singlephase control circuit energized by thevoltage to be regulated, a winding in said circuit, a single half-waverectifier in said circuit eiecting in said Winding intermittenthalf-wave current pulses, a regulating circuit, a switch in saidregulating circuit operated by said winding, and means operated by saidregulating circuit for varying the voltage of said system.

14. A voltage regulator for an alternating-current system, saidregulator comprising a singlephase control circuit energized by thevoltage to be regulated, a Winding in said circuit, a single half-waverectifier in said circuit eiecting in said winding intermittentfractional-Wave current pulses, a regulating circuit, a switch in saidregulating circuit operated by said Winding, and means operated by saidregulating circuit for varying the 4voltage of said system.

EDWIN W. SWANSON.

